• Transactions of The Korea Fluid Power Systems Society
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• 제5권2호
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• pp.14-19
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• 2008

Hydraulic excavator consists of booms, arms, bucket, and cylinder. The cylinder make these structures moved and the cushion parts of cylinder in operation absorb the great impact which is stemmed from high velocity and pressure at cushion parts of cylinders. The cushion technology of cylinders has a great effect on the operator's comfortable as well as protecting equipment from damage by suppressing the inertia of the hydraulic excavator. In this study, three hydraulic cylinders have different shapes of a cushion ring, respectively. we studied optimal cushion pattern by analyzing the change of cushion pressure and time, according to supply pressure and velocity variations.

• Structural Engineering and Mechanics
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• 제29권1호
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• pp.1-16
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• 2008

Tunnels are generally constructed below the ground water table, which produces a long-term interaction between the tunnel lining and the surrounding geo-materials. Thus, in conjunction with tunnel design, the presence of water may require a number of considerations such as: leakage and water load. It has been reported that deterioration of a drainage system of tunnels is one of the main factors governing the long-term hydraulic and structural lining-ground interaction. Therefore, the design procedure of an underwater tunnel should address any detrimental effects associated with this interaction. In this paper an attempt to identify the coupled structural and hydraulic interaction between the lining and the ground was made using a numerical method. A main concern was given to local hindrance of flow into tunnels. Six cases of local deterioration of a drainage system were considered to investigate the effects of deterioration on tunnels. It is revealed that hindrance of flow increased pore-water pressure on the deteriorated areas, and caused detrimental effects on the lining structures. The analysis results were compared with those from fully permeable and impermeable linings.

• Structural Engineering and Mechanics
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• 제61권4호
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• pp.497-510
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• 2017

A framed structure may be composed of two sub-structures, which are linked by a hinged joint. One sub-structure is the primary system and the other is the secondary system. The primary system, which is subjected to the periodic external load, can give rise to an auto-parametric resonance of the second system. Considering the geometric-stiffness effect produced by the axially internal force, the element equation of motion is derived by the extended Hamilton's principle. The element equations are then assembled into the global non-homogeneous Mathieu-Hill equations. The Newmark's method is introduced to solve the time-history responses of the non-homogeneous Mathieu-Hill equations. The energy-growth exponent/coefficient (EGE/EGC) and a finite-time Lyapunov exponent (FLE) are proposed for determining the auto-parametric instability boundaries of the structural system. The auto-parametric instabilities are numerically analyzed for the two frames. The influence of relative stiffness between the primary and secondary systems on the auto-parametric instability boundaries is investigated. A phenomenon of the "auto-parametric internal resonance" (the auto-parametric resonance of the second system induced by a normal resonance of the primary system) is predicted through the two numerical examples. The risk of auto-parametric internal resonance is emphasized. An auto-parametric resonance experiment of a ${\Gamma}$-shaped frame is conducted for verifying the theoretical predictions and present calculation method.

• Journal of Korea Water Resources Association
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• 제38권8호
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• pp.675-689
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• 2005

In this paper, it was analyzed the variation of hydraulic characteristics through changing discharge at main channel and lateral channel and state of hydraulic structure at the natural channel junction by experiment. The experimental area is chosen at the channel junction of Nam-Han river and Pyeongchang river. The scale of the experiment is 1/200 in horizontal, and 1/66.7 in vortical, so the distoration rate is 3. From the experiment, the reduction effect of the water level is $12\%$ in the case of removing intank dam, and $5\%$ at the hydro-electronic dam removing case. Furthermore, in the case of two hydraulic structures removing, the reduction effect of water level is $18\%$ at the channel junction. Also, the stagnation zone, which is cased diminution of the channel at the junction, is decreasing through removing the structures.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2017년도 학술발표회
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• pp.66-66
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• 2017

Hydraulic jump is typically designed to occur over low-haed dam spillways and weirs in the river. An important engineering application of the hydraulic jump is to dissipate the intense kinetic energy of the flows over such hydraulic structures. Turbulent flow and roller-like vortex riding up the free sureface of the jump cause most of the energy dissipation. We carry out a high resolution three-dimensional numerical simulations of a submerged hydraulic jump in a spillway and compare numerical results with a laboratory measurement obtained by the PIV. The numerical results further show the dynamic behavoirs of the inner and outer layers of the submerged wall-jet and the recirculating roller of the hydraulic jump.

• Journal of Ocean Engineering and Technology
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• 제21권4호
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• pp.21-27
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• 2007

The multiplication equipment of marine products with artificial upwelling structures could be useful in the fishing grounds near coastal areas. Artificial upwelling structures could move the inorganic nutrients from the bottom to the surface. Artificial upwelling structures have been used to improve the productivity of fishing grounds. Until now, research on artificial upwelling structures has been related to the distribution of the upwelling region, upwelling structures, and the marine environment. However, little work on the optimum design of the rubber-mound artificial upwelling structures has been done to increase the efficiency of drawing up the inorganic nutrients. This study investigated the optimum cross-section of rubber-mound artificial upwelling structures by means of hydraulic experiments. The hydraulic experiments include the falling test of rubber. Based on the results of the falling test, the relationship between the length of the rubber mound and water velocity, and the relationship between the shape of the rubber and the stratification parameter were established. In addition, the effect of the void ratio of various artificial structures on the stratification parameter was studied. From the experiment, it was found that upwelling could be enhanced when the ratio of structure height to water depth was 0.3 and stratification parameter was 3.0. The upwelling was not improved when the void ratio exceeded 0.43. The optimum size of rubber mounds was determined when the incident velocity was influenced by the mean horizontal length rather than size of block.

• Magazine of the Korean Society of Agricultural Engineers
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• 제11권4호
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• pp.1832-1840
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• 1969

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 1985년도 제27회 수공학연구발표회논문초록집
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• pp.203-207
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• 1985

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 1998년도 분과위원회 연구과업 보고서
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• pp.901-948
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• 1998

• Smart Structures and Systems
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• 제20권2호
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• pp.163-173
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• 2017

Structural health monitoring (SHM) of civil infrastructure using fiber Bragg grating sensor networks (FBGSNs) has received significant public attention in recent years. However, there is currently little research on the health-monitoring technology of high-piled wharfs in coastal ports using the fiber Bragg grating (FBG) sensor technique. The benefits of FBG sensors are their small size, light weight, lack of conductivity, resistance corrosion, multiplexing ability and immunity to electromagnetic interference. Based on the properties of high-piled wharfs in coastal ports and servicing seawater environment and the benefits of FBG sensors, the SHM system for a high-piled wharf in the Tianjin Port of China is devised and deployed partly using the FBG sensor technique. In addition, the health-monitoring parameters are proposed. The system can monitor the structural mechanical properties and durability, which provides a state-of-the-art mean to monitor the health conditions of the wharf and display the monitored data with the BIM technique. In total, 289 FBG stain sensors, 87 FBG temperature sensors, 20 FBG obliquity sensors, 16 FBG pressure sensors, 8 FBG acceleration sensors and 4 anode ladders are installed in the components of the back platform and front platform. After the installation of some components in the wharf construction site, the good signal that each sensor measures demonstrates the suitability of the sensor setup methods, and it is proper for the full-scale, continuous, autonomous SHM deployment for the high-piled wharf in the costal port. The South 27# Wharf SHM system constitutes the largest deployment of FBG sensors for wharf structures in costal ports to date. This deployment demonstrates the strong potential of FBGSNs to monitor the health of large-scale coastal wharf structures. This study can provide a reference to the long-term health-monitoring system deployment for high-piled wharf structures in coastal ports.